The axillary region is a body area with unique odor-producing characteristics. In the axillae; apocrine, sebaceous, eccrine and apoeccrine glands provide substrate for a large permanent population of microorganisms. Numerous studies have suggested that axillary secretions can convey information between individuals or groups of people. These odors allow individuals to identify their own odor as well as those of their spouse and close genetic kin. In addition, studies from our laboratory have shown that ethanol extracts made from male and female axillary secretions can change the length and timing of the human female menstrual cycle. Consequently, axillary secretions and their odors appear to be the best documented human odor source with chemical communicatory properties. Despite the fact that axillary secretions and their odors can convey information between individuals and/or groups of people, little information has been published concerning the structural nature of the axillary odors and the biochemical pathways that produce them. Previous studies of axillary odors have suggested that the volatile steroids and isovaleric acid are major contributors to the characteristic axillary odor. Our recently published studies have determined the nature of the axillary odors, in a combined male sample; they are C6 to C11 saturated, unsaturated and branched acids, with (E)-3-methyl-2-hexenoic acid being the largest component present. Our proposed studies will examine the odoriferous components in individual male and female subjects and document changes in these compounds across the menstrual cycle. The proposed study will also further characterize the proteinaceous precursors to the major axillary odorant: 3-methyl-2-hexenoic acid. We now have raised antibodies to both of the apocrine secretion odor binding proteins and will use these in an affinity column to obtain larger amounts of these compounds. The fact that a characteristic human odor is secreted onto the skin bound to proteins is a novel finding. It suggests that if the odors which characterize the axillae are responsible for the primer pheromone activity reported for axillary extracts (e.g., menstrual cycle alteration), the chemistry involved may be similar to other mammalian pheromone systems.